Answer:D. 36 m
Step-by-step explanation: Use the Pythagorean Theorem, which is a^2 + b^2 = c^2 to find the missing side. C is the hypotenuse. Plug in the numbers.
15^2 + b^2 = 39^2
Simplify.
225 + b^2 = 1521
Subtract 225 from each side.
b^2 = 1296
Square root each side to isolate b.
b = 36
The height of the support beam is 36 m.
